Although many disease-associated mitochondrial DNA (mtDNA) mutations ha been characterized. the relationship between the mutant genotype and respirators phenotype remains to be clarified in many cases. The availability of patient cells and cybrids that contain patient mitochondria. and newly developed techniques to study mitochondrial complexes, provide novel approaches to address this problem.
It is intended to test the pathogenicity of mtDNA mutations. Firstly by attempting to complement a mutant mitochondrial gene. which will entail transfecting patient cells with a code corrected version of the defective mitochondrial gene. Secondly by transfecting normal cells with a mutant mitochondrial gene. If, the synthetic genes alter the respiratory phenotype this will provide the strongest evidence to date of a causal role for mtDNA mutations in human disease. Moreover, in the longer term this strategy could offer a novel route to gene therapy of mitochondrial diseases.